ISOCAM Interactive Analysis User's Manual Version 5.0 - ISO - ESA

22.1. JITTER CORRECTION 295
du
0.20
0.10
0.00
-0.10
-0.20
-0.30
-0.40
0 20 40 60 80 100
CUBE
Figure 22.2: Comparison of jitter computation methods. Jitter offsets computed with the gauss
method are represented by the solid line, and jitter offsets computed with the psf method are
represented by the dashed line. The data used in this example are from an observation using
the 1.5 ′′ PFOV and the LW7 filter.
scd
This keyword is used to select all the IMAGEs corresponding to a particular CAM STATE
( ISO pointing ) from the PDS CUBE. By default all STATEs are selected.
display Setting display = 1 will display an averaged fit per CAM STATE. Setting display =
2 will display the each fit of each IMAGE.
verb Setting verb = 1 will output the averaged fit parameters per CAM STATE. Setting verb
=2will output the fit parameters per IMAGE.
method Select fitting method. The default is method = ‘gauss’ .
bsize
See description of algorithm above. The default depends on the selected method.
col24 Set to remove column 24 ( actually column 23 in IDL convention ) from IMAGEs before
fitting.
nterms
fit.
Only applies to method = ‘gauss’ . Select the number of terms used in the gaussian
22.1.2 Applying jitter offsets
The application of the jitter offsets du, dv is the most difficult part of jitter correction. Currently,
two methods exist and neither are really effective. These methods are implemented with reduce
and project cube.pro
reduce We can attempt to correct the jitter by shifting each IMAGE by du, dv before averaging
to an EXPOSURE. The limitation of this method is the shifting algorithm. So
far all attempts to perform sub-pixel shifting causes some smoothing and this defeats
the purpose of removing the jitter. After jitter computation with compute jitter jitter
correction with reduce can be attempted with